1. Field of the Invention
This invention relates to an apparatus for stabilizing the transport of a material web, in particular a fibrous web, which is guided on the top side of a covering whereby the apparatus is arranged on the bottom side of the covering and, looking in the web running direction, is directly in front of an intake nip formed by a roller and the covering.
2. Discussion of Background Information
In particular in the case of high web speeds, in the case of structured coverings with a rough and coarse top side and in the case of thin and light fibrous webs such as tissue webs there is a problem in that the guided material web is often lifted off the covering in the region of an intake nip formed by a roller and the covering, resulting in the formation of stripes and creases and, consequently, poor winding quality.
The reason for this is that rough meshes, for example, are very voluminous and therefore carry a great deal of air not only on the inside but also on the outside in the form of a boundary layer of air. When a material web guided on such a mesh runs into the intake nip formed by the mesh and a roller, the boundary layer of air carried along with the mesh is compressed in the intake nip on account of the shrinking volume, leading therein to the generation of a positive pressure which expends itself through the air-permeable mesh, thus resulting in the material web being lifted off. This effect arises in particular in the case of light material webs such as tissue webs.